Modern air vehicles contain many miles of electrical power and signal wiring. Wiring is costly to install, heavy, and vulnerable to damage from service (i.e., incorrectly routed near hot equipment and/or bundled together with other incompatible wire types such as soft wire laying adjacent to hard wire, etc.) and maintenance. Moreover, all wire deteriorates in service due to environmental factors such as: extreme heat and cold temperature swings, humidity, salt damage associated with marine environments, contamination by aircraft fluids (i.e., fuel, oil, hydraulic fluid, de-icing fluid, cleaning chemicals, toilet residue, galley spillage, etc.), as well as in-flight vibration causing chafing of wires rubbing against other wires or the structure of the aircraft.
The above-described electrical power and signal wiring are typically provided through a wire harness (a.k.a. cable harness), which typically bundles a collection of cables and/or wires that transmit informational signals (“signals”) or operating currents (“power”) from one point to another. These wires and/or cables are often bound together to form a harness using, for example, clamps, cable ties, cable lacing, sleeves, electrical tape, conduit, a weave of extruded string, or a combination thereof. On most aircraft, wire bundles contain many different wires with several different types of insulation. Typically, wire bundles are composed of AC power cables, DC power cables, signal (circuit controlling) wires, and circuit ground wires. Also, there are bundles that carry power from different power sources (busses). These conditions make it extremely difficult to protect any circuit in such a bundle, where an insulation failure could result in an electrical problem that has multiple power sources and current paths to feed it. A wide variety of problems arise including shorting, arcing, or some other type of damage to a bundle with this mix of wires.
In addition to air vehicles (e.g., spacecraft, and aircraft), wire harnesses are used in automobiles, motorcycles, trains, ships, and boats. Indeed, vehicles typically contain many masses of wires that may stretch over several miles if fully extended. Binding the wires and cables into harnesses better secures them against the adverse effects of vibrations, abrasions, and moisture. By constricting the wires into a non-flexing or semi-flexing bundle, usage of space is also increased, and the risk of a short circuit is greatly decreased. Similarly, installation time is decreased since an installer must install only a single harness (as opposed to multiple loose wires). In certain situations, the wires may be further bound into a flame-retardant sleeve that lowers the risk of electrical fires.
While the wire harnesses provide several advantages over loose wires and cables, wire harnesses still suffer from the above deficiencies. For example, in aviation, weight is a crucial factor and, as new military and civilian aircraft systems are developed, wire harnesses account for increasingly larger mass fractions of the aircraft's total weight. Similarly, for new military and civilian aircraft platforms, there is a continuous drive to simultaneously improve performance while reducing costs. Another drawback of traditionally bound wire harnesses is the clutter and space inevitably occupied by the wire bundles. Furthermore, current aircraft development emphasizes electrical systems that enhance the overall performance of the platform. This includes state-of-the-art systems such as fly by wire, electro-hydraulic actuators, distributed sensor systems and high power payloads. With the increased demand on electrical components have come increasingly complex installations and maintenance. Current efforts to reduce the weight and complexity of these systems center on moving from cables to high-speed serial architectures, switching from hydraulic to electrical systems, and distributed architectures. Not surprisingly, these efforts require an increased emphasis on harness materials and design while significantly reducing harness mass fraction; a task that cannot be accomplished with traditional wire harnesses. Finally, traditional wire harnessing techniques typically require specific components to secure harnessing (e.g., wires, and other conductors) along the length of a structure (e.g., fuselage, wing, etc.) and other features, such as holes or conduits, that facilitate passing the harnessing through a structure, such as ribs and bulkheads.
Thus, what is needed is an economical, lightweight wire harness capable of being embedded within or integrated with the structure and/or body panel of a vehicle. Embedment of these conductor systems in composite structure during manufacture may significantly reduce cost, weight, improve reliability, and most significantly, reducing the factor of safety (i.e., systems such as fly by wire (“FBW”) aircraft would benefit greatly by allowing for improved redundancy and increased safety).
As will be discussed in greater detail below, such embedded wire harnesses may be facilitated using carbon nanotubes (“CNT”) material, carbon nano-filaments (“CNF”) material, fiber-reinforced plastic (“FRP”), fiber metal laminate (“FML”), metal deposited polyester nonwoven material (e.g., Nickel/Copper Polyester Nonwoven, and nickel chemical vapor deposition (“NiCVD”) coated fibers), or a combination thereof. For example, one or more conductors (e.g., CNT, CNF, NiCVD, etc.) may be sandwiched between two or more insulating layers of material such that the conductor is electrically isolated and structural loads can be passed through the conductor sandwich assembly (“CSA”). The CSA may be incorporated either into or onto a composite structure without detrimental effect to the electrical and structural properties of the incorporated system.